In principle, the DSW solution for any nonlinear, dispersive wave equation with a modulationally stable periodic wave solution
can then be found. However, most nonlinear, dispersive wave equations are non-integrable. While it is still difficult
to determine the full DSW structure for non-integrable equations, a general method exists to find its solitary wave and
linear dispersive wave edges if the DSW is of “KdV-type,” that is it consists of a monotonic modulated periodic wavetrain
with solitary waves at one edge and linear dispersive waves at the other [1]}, [2]}. The reason that this can
be done is that for a modulationally stable, nonlinear, periodic dispersive wave, its modulation equations are degenerate at
these two edges and have a standard structure, which can be determined without detailed knowledge of the full modulation
equations [1]}, [2]}.
